JP3048461B2 - Method for producing grinding wheel for electrolytic dressing containing submicron abrasive grains - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grindstone used for grinding and polishing, and more particularly to a method for producing a conductive grindstone which is dressed by an electrolytic effect.

[0002]

2. Description of the Related Art An electrolytic dressing method and apparatus for a conductive grindstone, which uses a conductive grindstone such as a cast iron fiber bond diamond grindstone, applies a voltage to the grindstone and dresses the grindstone by electrolysis, has been disclosed by the same applicant as the present applicant. JP
It is disclosed in Japanese Patent Application No. 1-188266 (Japanese Patent Application No. 63-12305) and succeeded in mirror-polishing semiconductor materials such as silicon as electronic materials. Further, an electrolysis in-process dressing grinding method (Electrolytic Inproc
A method and apparatus referred to as “ess dressing: Elid grinding method” have been developed and published by the applicant of the present invention (RIKEN Cymbodium, “Latest Technology Trend of Mirror Surface Grinding”, held on March 5, 1991).

[0003] The Elid grinding method comprises a grindstone having a contact surface with a workpiece, an electrode facing the contact surface, a nozzle for flowing a conductive liquid between the grindstone and the electrode, and a voltage between the grindstone and the electrode. Is a device comprising a power source and a power supply for applying the voltage, applying a voltage between the grindstone and the electrode while flowing a conductive liquid between the grindstone and the electrode, and dressing the grindstone by electrolysis.

FIG. 6 shows a dressing mechanism by the Elid grinding method. At the beginning of sharpening of the grinding wheel (A), the electric resistance between the grinding wheel and the electrode is small and a relatively large current (5
-10A) flows. As a result, the metal part (bond) on the surface of the grindstone is dissolved by the electrolytic effect, and the non-conductive diamond abrasive grains protrude. In addition, when energization is continued, iron oxide (F
An insulating film mainly composed of e ₂ O ₃ ) is formed on the grindstone surface, and the electric resistance of the grindstone increases. This reduces the current,
Dissolution of the bond is reduced, and the protrusion of the abrasive grains (sharpening of the grinding stone) is substantially completed (B). When the grinding is started in this state (C), the diamond abrasive grains are worn as the workpiece is ground while the coating releases grinding dust. When grinding is further continued (D), the insulating coating on the grindstone surface is removed by abrasion, the electric resistance of the grindstone decreases, the current between the grindstone and the electrode increases, the dissolution of the bond increases, and the protrusion of the abrasive grains (grindstone) ) Is resumed. Therefore, during the grinding by the Elid grinding method, the overelution of the bond is suppressed by forming and removing the coating as shown in (B) to (D), and the protrusion of the abrasive grains (grinding of the grindstone) is automatically adjusted. You. The above-described cycle shown in (B) to (D) is hereinafter referred to as an Elid cycle.

[0005]

It has been found that the finer the abrasive grains contained in the grinding wheel, the better the finished surface obtained by the above-mentioned Elid grinding can be obtained. In Elid grinding, the grinding wheel is not clogged by the above-mentioned Elid cycle even if the abrasive grains are made fine. Therefore, in order to obtain a very excellent processed surface such as a mirror surface by grinding, it is desirable that the abrasive grains be as fine as possible.

However, the average grain size of the abrasive grains is submicron,
For example, at about 50 °, it was extremely difficult to disperse the abrasive grains in the grindstone. Therefore, no attempt has been made to manufacture a grinding wheel for electrolytic dressing containing submicron abrasive grains. Further, the grinding surface of such a grindstone requires a certain area according to the size of the workpiece. In particular, in order to grind a semiconductor or the like, which has been increasing in demand in recent years, a grindstone having a diameter of at least about 200 mm is required. However, the production of a grindstone for electrolytic dressing containing such large-area submicron abrasive grains is almost impossible. It was thought possible.

Therefore, the present invention solves such a problem,
An object of the present invention is to provide a method for producing a grinding wheel for electrolytic dressing having a large area and containing submicron abrasive grains.

[0008]

According to the present invention, a mixed powder is prepared by kneading a cobalt metal powder having a particle size of several μm and a diamond powder having a particle size of 1 μm or less, and mixing the mixed powder in a predetermined female mold. Forming a molded body by compression molding, sintering the molded body to form a whetstone segment, and bonding the whetstone segment to a base plate with a conductive adhesive, the electrolytic dressing comprising: There is provided a method of manufacturing a grinding wheel for use in a vehicle.

According to an embodiment of the present invention, the kneading step preferably comprises adding a predetermined amount of diamond powder little by little while periodically pressing a push rod against a predetermined amount of metal powder. Preferably, the diamond powder has an average particle size of about 50 ° or less.

[0010] Further, the compression molding step includes a contact pressure of 6 to 8 t.
/ cm ² , and the sintering step is preferably performed at a temperature of 1000 ° C. or higher.

[0011]

According to the above-described method for manufacturing a grinding wheel according to the present invention, cast iron, which has conventionally formed a bond, is changed to relatively soft cobalt, and this cobalt metal powder and diamond powder having a particle size of 1 μm or less are kneaded in advance. Therefore, the fine diamond powder can be captured on the surface of the relatively large cobalt metal powder and dispersed relatively uniformly. This effect is particularly great when diamond powder having an average particle size of about 50 ° or less is added little by little while periodically pressing a push rod against metal powder having a particle size of several μm.

Further, a large grinding wheel can be manufactured from a small segment by a step of sintering the formed body to form a grinding wheel segment and bonding the grinding wheel segment to a base plate with a conductive adhesive. Therefore, according to the present invention, it is possible to provide a method for producing a large-area electrolytic dressing grindstone containing submicron abrasive grains.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing Elid lap grinding using a grindstone manufactured according to the present invention. In this figure, reference numeral 10 denotes a substantially disk-shaped conductive grindstone having a vertical axis, which is rotatably mounted around the axis with a processing surface 12 facing upward by a driving device (not shown).

Above the grindstone 10, a rotatable drive shaft 14 of a processing machine is provided on an upper head of a processing apparatus (not shown). The drive shaft 14 is adapted to move in a horizontal direction and / or a vertical direction. A workpiece, that is, a work 16 is fixed to the lower surface of the drive shaft 14 in a generally known manner. The upper surface of the grindstone 10, that is, the contact surface 12 with the work 16 is a horizontal cutting surface, and the rotating contact surface 12 comes into contact with the work 16 to cut the work 16.

An electrode 20 is provided above a portion of the grindstone 10 that does not contact the work 16 with a gap facing the contact surface 12 of the grindstone 10. A plurality of nozzles 30 are provided around the grindstone 10, and a weakly conductive grinding fluid, that is, a coolant, flows between the grindstone 10 and the electrode 20 via a supply pipe 32. It is preferable that the nozzle 30 be provided so that the coolant flows between the grindstone 10 and the work 16.

Further, the apparatus is provided with a power supply 40,
A positive voltage can be applied to the grindstone 10 and a negative voltage can be applied to the electrode 20 via the power supply 42 that comes into contact with the lower surface of the grindstone 10. This power supply 40
A pulse power supply or a power supply in which pulse and DC are mixed is preferable. In use, the workpiece 16 is ground by the cycle of protrusion (A) of the grinding wheel, formation of the film (B), grinding (C), and wear of the abrasive grains (D) by the above-described Elid grinding method.

In order to manufacture the grindstone 10, first, a particle size of several μm is used.
m of cobalt metal powder and diamond powder having a particle size of 1 μm or less are kneaded to form a mixed powder. In this kneading, it is preferable to add the diamond powder little by little while periodically pressing the push rod against the metal powder. In this case, the amount of diamond powder is preferably about 25 (about 1.1 carat / cm ³ ). The diamond powder has an average particle size of about 50Å.
The following should be good. By this step, the fine diamond powder can be captured on the surface of the relatively large cobalt metal powder and dispersed relatively uniformly.

Next, the obtained mixed powder is compression-molded in a predetermined female mold to produce a molded body. This compression molding step is preferably performed at a surface pressure of 6 to 8 t / cm ² . The female concave shape may be any of a rectangle, a circle, a sector, an ellipse, and the like. It is generally difficult to pressurize a large area with a uniform surface pressure. In addition, since pressing a large area at one time requires a pressing device with a very large output, the size of the female mold is limited to the whetstone 10. It is preferable that the contact surface 12 is divided into small areas.

Next, the obtained compact is sintered to form a grinding wheel segment. This sintering is performed at a temperature of 1000 ° C. or more, preferably 1100 to 1200 ° C. Next, the grindstone segments are bonded to the base plate with a conductive adhesive, and the desired grindstone 1 is formed.
Get 0. With this manufacturing method, a large grinding wheel can be manufactured from a small segment. Example 1 A grindstone (diameter: 215 mm) shown in FIG. 2 was manufactured in the following procedure.

First, while a pressing rod was periodically pressed against cobalt metal powder having a particle size of several μm, diamond powder of # 3 million fine particles (average particle size: about 50 °) was added little by little to prepare a mixed powder. The amount of diamond powder is 2
5 (approximately 1.1 carats / cm ³ ). Next, the obtained mixed powder was compression-molded in a predetermined female mold to form a molded body. For this compression, a press having an output of 60 t was used. The concave shape of the female mold is almost square and the area is about 25 mm ²
Met. Next, the obtained molded body was sintered at 1100 to 1200 ° C. to form a grinding wheel segment. The thickness of the obtained whetstone segment was about 5 mm.

In the same manner, grinding stone segments having the same dimensions were prepared using # 8000 fine diamond powder. Further, a grinding wheel segment of the same size was prepared using # 3 million fine particles in half the area and # 8000 fine particles in the other half. Next, the grindstone segments in contact with the inner and outer surfaces of the grindstone were cut in advance by wire cutting, and the respective grindstone segments were adhered to the base plate with a conductive adhesive to obtain the grindstone shown in FIG. It is preferable that the gap between the segments is as small as possible, and in this prototype, it was 1 mm or less. An adhesive containing silver powder was used as the conductive adhesive.

The surface of the obtained grindstone had no gloss in the # 3 million fine particle portion. Next, using the grinding wheel obtained in the above-described process, Elid grinding was performed using a grinding machine, a power source, a work material, and the like shown in Table 1. The results are shown in FIGS.

[0023]

[Table 1]

(1) Dressing characteristics As with the conventional apparatus, there was a decrease in the actual current with the energization time, but a relatively high electrolysis current was confirmed by vigorous electrolysis of the cobalt bond (FIG. 3, mark ●). It was confirmed that the roughness of the surface increased and the coating was formed on the grindstone surface due to the electrolysis. (2) Mirror surface grinding characteristics Fig. 4 shows how the processing load changes. There was little load reduction due to spark-out, and it was easy to maintain a constant pressure after cutting. (3) Roughness of machined surface Fig. 5 shows the roughness pattern of the cemented carbide finished surface. In particular, an excellent mirror surface having an Rmax of 110 ° was obtained although it was sensitive to the processing heat and vibration. Example 2 In Example 2, similarly to the manufacturing process of Example 1, a grindstone manufactured by changing the concentration of diamond powder to about 15 was applied to cemented carbide and optical glass. The results are shown in FIGS. Here, the grinding machine, Elid power supply, grinding fluid and truer are the same as in Table 1. As a measuring instrument used for evaluating the mirror-finished surface roughness, the same grinding resistance measurement system (manufactured by Cosmo Design Co., Ltd.) as in Example 1 was used for cemented carbide, and laser light roughness was generally used for optical glass. W called total
YKO: TOPO-3D (Shosho Kiki Co., Ltd., imported and handled) was used. (1) Dressing Characteristics The electrolytic dressing characteristics shown in FIG. 7 were stable at a relatively high current, although the current decreased, as in FIG. 3 of Example 1. Since the concentration of the grindstone after the electrolysis was reduced from 25 to 15 in the initial state, the grindstone exhibited silver white in the initial state with less pores than in Example 1, and then exhibited a reddish black when the coating was formed. did.

FIG. 8 shows a change in coating thickness in the main lap grinding. The initial coating thickness is about 86 μm, # 1200
The grinding wheel does not return to its original size even after removing the pre-grinding traces. (2) Mirror Surface Grinding Characteristics FIGS. 9 and 10 show how the machining load of the cemented carbide and the optical glass changes. In the case of cemented carbide, when a spark was cut out after forcible cutting to about 19 kgf, the load decreased slightly, and processing was completed in about 40 minutes. The glass could be processed with low load (Elid: 3-4A).

FIG. 11 shows an elemental analysis of the coating produced by X
2 shows the results measured with a line microanalyzer. Co in the bonding material is mainly detected, and then Cu from the electrodes and the like, Mo from the grinding fluid, and F eluted from a part of the grinding machine.
e has been detected. (3) Finished Surface Roughness FIG. 12 shows the finished surface roughness pattern of the cemented carbide, and FIG. 13 shows the finished surface roughness of the optical glass. As a result of six measurements,
An average of about 70 ° Rmax (54-108 °) was achieved with cemented carbide. In the case of optical glass, about 84 Rmax (68-100 °) was obtained in about 20 minutes.

From the above, the pre-processed surface by # 1200 and #
Compared with the mirror-finished surface of 3 million, the former had a peeling surface but the latter did not.

[0028]

According to the above-described method for manufacturing a grindstone according to the present invention, cast iron, which has conventionally formed a bond, is changed to relatively soft cobalt, and this cobalt metal powder is mixed with a 1 μm particle size.
m or less in advance, the fine diamond powder is captured on the surface of the relatively large cobalt metal powder and can be dispersed relatively uniformly. This effect is particularly great when diamond powder having an average particle size of about 50 ° or less is added little by little while periodically pressing a push rod against metal powder having a particle size of several μm.

Further, a large grinding wheel can be manufactured from a small segment by a step of sintering the formed body to form a grinding wheel segment and bonding the grinding wheel segment on a base plate with a conductive adhesive. Therefore, according to the present invention, it is possible to provide a method for producing abrasives for electrolytic dressing having a large area and containing submicron abrasives.

[Brief description of the drawings]

FIG. 1 is a view schematically showing an electrolytic dressing process using a grindstone manufactured according to the present invention.

FIG. 2 is a diagram showing dimensions of a prototype grinding wheel.

FIG. 3 is a view showing electrolytic dressing characteristics of a prototype grinding wheel.

FIG. 4 is a diagram showing a change in processing load by a prototype grinding wheel.

FIG. 5 is a diagram showing surface roughness after Elid grinding.

FIG. 6 is an explanatory view showing an Elid cycle in the Elid grinding method.

FIG. 7 is a diagram showing electrolytic dressing characteristics of a second prototype grinding wheel.

FIG. 8 is a diagram showing a change in coating thickness in main lap grinding using a second prototype grinding wheel.

FIG. 9 is a view showing a change in processing load of a cemented carbide by a second prototype grinding wheel.

FIG. 10 is a diagram showing a change in processing load of optical glass by a second prototype grinding wheel.

FIG. 11 is a diagram showing the results of elemental analysis of the generated coating measured by an X-ray microanalyzer.

FIG. 12 is a view showing a finished surface roughness pattern of a cemented carbide.

FIG. 13 is a view showing a finished surface roughness pattern of the optical glass.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Whetstone 12 Contact surface 14 Drive shaft 16 Work 20 Electrode 30 Nozzle 40 Power supply 42 Power supply

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI B24D 5/06 B24D 5/06 (58) Field surveyed (Int.Cl. ⁷ , DB name) B24D 3/34 B24D 3/00 320 B24D 3/00 330 B24D 3/00 340 B24D 3/06 B24D 5/06

Claims (4)

(57) [Claims] 1. Cobalt metal powder having a particle size of several μm and a particle size of 1.
μm or less of diamond powder is kneaded to form a mixed powder, the mixed powder is compression-molded in a predetermined female mold to form a compact, and the compact is sintered to form a grindstone segment. And a method of manufacturing a grindstone for electrolytic dressing, comprising the steps of: adhering to a base plate with a conductive adhesive. 2. The method according to claim 1, wherein the kneading step comprises adding a predetermined amount of diamond powder little by little while periodically pressing a push rod against a predetermined amount of metal powder. Production method. 3. The diamond powder has an average particle size of about 5
The method according to claim 2, wherein the angle is 0 ° or less. 4. The compression molding step includes a contact pressure of 6 to 8 t / cm ^2.
The method according to claim 3, wherein the sintering step is performed at a temperature of 1000 ° C. or higher.